1. Field of the Invention
The invention relates to a method of and an apparatus for guiding at least one steel wire from a furnace into a lead bath, which method is carried out in such a manner that lead drag-out from the lead bath is avoided as much as possible.
2. Discussion of the Related Art
The use of lead tanks or lead baths for heat treatments is sufficiently known in the state of the art. Everywhere where these lead tanks or lead baths are used, one is faced with the problem of lead drag-out. That is, along with the objects to be treated such as steel wires, lead is dragged out of the lead tanks or lead baths in the form of lead drops, whether or not enveloped in a lead-oxide skin. This results in different drawbacks. In the first place, there is the known harmful effect on health and the environment. Further, there is also a qualitative drawback in the sense that the baths located downstream of the lead bath are "poisoned" by the lead particles dragged along. This does not benefit the quality of the treatment connected with these baths downstream. Moreover, wire products for certain applications do not tolerate lead drag-out, for instance those wire products that are electrolytically coated afterwards. Finally, there is the considerable loss of lead itself.
The problem of lead drag-out is a complex problem and presents chemical, physical as well as mechanical aspects.
Therefore, the state of the art presents different solutions to avoid lead drag-out.
Thus, it is sufficiently known from U.S. Pat. No. 3,669,761 to cover the end of the lead bath with a coal bed to avoid the formation of lead oxides (Pb.sub.x O.sub.y). Indeed, lead oxides have the property of being more viscous than lead at the temperatures that prevail at the end of the lead bath, and they are more readily than lead dragged out of the lead bath along with the wires. They also drag pure lead along in the process. A further purpose of the lead bed is to mechanically stop the lead dragged along.
However, despite these well known measures, lead drag-out has remained a major problem wherever lead baths are used.